Cutter insert for rock bits

ABSTRACT

A carbide cutter insert for a rock bit body is strengthened against breakage and its removal and replacement are facilitated by encasing the insert in a protective jacket of material substantially softer than the carbide. The composite element is then firmly pressed and/or bonded in an orifice in the cutting face of the bit body. The element can be readily removed simply by cutting away the softer jacket by a suitable machine tool operation without damaging the body bore.

United States Patent Gardner [45] Sept. 26, 1972 154] CUTTER INSERT FORROCK BITS 3,618,683 11/1971 Hughes 175/410 [72] Inventor: Jimmy D.Gardner, HOUSIOH, Tex. FOREIGN PATENTS OR APPLICATIONS [731 Assign:Missim' Manmcmring Cmnpany, 70,945 10/1942 Norway ..175/410 203,1228/1956 Australia ..175/410 [22] Filed: Sept, 4, 1969 683,018 1 1/1952Great Britain ..175/410 [21] Appl' 855208 Primary Examiner-James A.Leppink Attorney-Bertram H. Mann, Frank B. Pugsley, James [52] U.S. Cl..175/410 Ulmer. Delmar Sroufe n Larry l m n [51] Int. Cl ..E21c13/0l[58] Field of Search 175/410, 413; 299/92 [57] ABSTRACT A carbide cutterinsert for a rock bit body is [56] References cued strengthened againstbreakage and its removal and UNITED STATES PATENTS replacement arefacilitated by encasing the insert in a protective jacket of materialsubstantially softer than 2,842,342 7/1958 B "175/410 the carbide. Thecomposite element is then firmly 3,268,259 8/1966 Snipe ..175/410pressed and/Or bonded i an fi in the cutting f 3,342,531 9/1967 Krekeler..175/410 of the bit body The element can be readily removed 3,342,5329/1967 Krekeler ..175/410 simply by Cutting away the Softer jacket by asuitable 3,357,507 12/1967 Steuvart ..175/410 machine tool operationwithout damaging the body 3,388,757 6/1968 Flttmger ..175/410 bore.3,397,012 8/1968 Krekeler ..299/92 1,522,593 1/1925 Pickin ..175/413 3Claims, 17 Drawing Figures PATENIEMzrzs I972 SHEET 1 BF 3 INVENTOR.

ATTORNEY CUTTER INSERT FOR ROCK'BITS I BACKGROUND OF THE INVENTION Manyrock bits, both of the solid and rotary type, are

provided with hardened cutter inserts, usually of tungare secured inplace by silver soldering so that they may be replaced. However, thelarge difference in thermal expansion betweenthe carbide inserts and thesteel body causes cooling cracks, .and the poor surface wettability ofthe carbide by the solder often results in poor bond coveragepercentage. On the other hand,'if the carbides'are securedin place bypress fitting, they cannot be removed. In that case, the entire bit isthrown away when the inserts have become'dull or broken. These insertsare quite brittle. and their exposed parts fracturable by glancingblowsplacing the material under tension. This condition is aggravated bythe fact that the mounting orifices in the bit body usually. areslightly bell-mouthed due to the methods of formation.

Accordingly, an object of the present invention is to providemeans forfirmly mounting carbide cutterinserts in rock bit bodies whilefacilitating removal of .the

inserts to facilitate their replacement and thus avoid the necessity ofscrapping the entirebit body whenthe inserts become dull.

Another object is to provide means for strengthening such carbideinserts.

Still another object is to provide a novel method of constructing acarbide insert composite.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings whichillustrate'a the -invention,

FIG. 1 is a partial transverse longitudinal. section through asolid-type rock bit embodying one form of the invention.

FIG. 2 is an enlarged longitudinal section through one of the cutterinsert composites.

'FIG. 3 is an end view of the structure in FIG. 2.

FIG. 4 is an enlarged view of a detail of FIG. I and showing thecomposite seated in an orifice in the bit body.

FIG. 5 is a viewsimilar to FIG. 4 but showing prior practice in somewhatexaggerated form.

7 FIG. 6 is a partial forward end view of a rock bit as in FIG. 1, butshowing a slight modification.

FIG. 7 is a detail section taken substantially on line 7-7 of FIG. 6.

FIGS. 8 and 9 are longitudinal sections showing two different forms ofarmored carbide composites in an initial assembly stage.

FIG. 10 is an end view of the structure in FIG. 8.

FIG. 1 l is a view of the structure in FIG. 8 after being driven into amatching orifice in the bit body.

FIG. 12 shows a driving tool being applied to a further modified cuttercomposite.

FIG. 13 is a perspective view of a further modified cutter composite.

FIG. 14 is a perspective view of a composite along the lines of that inFIG. 13 but showing a different form of carbide cutter element.

FIG. 15 is a longitudinal section through an armored carbide element ina preliminary stage of manufacture and illustrating a method of makingthe carbide inserts.

FIG. 16 is a detail cross section illustrating still another form ofcutter insert composite.

FIG. 17 is a section taken on line 17-17 of FIG. 16.

'DESCRIPTION'OF THE PREFERRED EMBODIMENTS FIG. 1 shows a more-or-lessconventional, solid type anvil-bit combination including a shank portion20 forming part of the anvil of a percussion type drill motor, and a bitbody portion 21 having a forward cutter face, generally designated 22.As best shown in FIG. 6,

srthe bodyis provided with wings 23, 24, and 25 terminating inperipheral chamfers 26 and inner chamfers and various known types of bitbodies, either solid or rotary, maybe utilized in connection with theinvention ,as hereafter described.

FIGS.'2, 3, and 4 illustrate in substantial enlargement one of thecomposite cutter inserts, say, one of the peripheral inserts 28. At thecenter of the insert there is :provided a generally cylindrical tungstencarbide cutter element 39 having a suitably shaped in this instance,

composite-then press fitted within orifice 43. However,

itv may befound desirable to sweat sleeve 41 into element 39,,that is,by heating and cooling of the sleeve,

- and also sleeve 41 may besilver soldered in orifice 43 withouttheformation of thermal expansion cracks previously mentioned. In any case,the bottoms of sleeve 41 and carbide element 39 should be firmly seatedagainst the bottom of orifice 43. It willbe observed, that sleeve 41projects somewhat beyond the mouth of orifice 43 and along the exposedpart of car- -bide button element 39, thus, providing reinforcement forthe button. In addition, the carbide element will be held by the-sleevefirmly in compression so as to be thereby further strengthened.Preferably, the sleeve should be made of steel having a high yield pointand high ductility to accommodate and withstand the high compressiveforces.

FIG. 3 shows a small radial longitudinal groove 44 formed in, the outersurface of cylindrical sleeve 41. This serves two purposes. In the firstinstance, it provides a relief vent for air trapped in orifice 43 duringthe pressing of the composite element into position therein.Furthermore, the slot facilitates release of the carbide buttonelementin that sleeve 41, of steel or other drillable material softer than thecarbide button 39, which is substantially notmachinable may be cut awayby a trepanning or other machine tool operation to release the button.The machining need out only to the bottom of groove 44, as suggested bydot-dash line 45, so the hole wall will not be affected leaving a splitsleeve extending around the hole when the remainder of sleeve 41 is cutaway. This remainder split sleeve can be readily collapsed and removedwithout damage to bore 43.

FIG. 5 illustrates prior practice in which a substantial part of carbidebutton element 39a is exposed outwardly of the bell mouth 43b of orifice43a in bit body 210. The peripheral cutter elements 28 and others at thegauge surface of the bit body'are especially subject to glancing blowswhich heretofore have caused breakage of these carbides with resultantdeterioration of the bit cutting capacity. Sleeve 41 of FIG. 2 does notpresent'a bell mouth because his initially longer than shown and is cutoff after the pressing operation. This does not reduce the effectivecutting life of the carbide, since the material of the sleeve, beingsofter than the carbide, wears away first so as to continuously exposeadditional carbide until the element is fully worn out.

FIGS. 6 and 7 illustrate a modified cutter insert assembly and means forlocking the same in position in a bit body. In thisinstance, the carbideelement 39b is mounted in the forward, cup-like orifice 46 of aconveniently cylindrical rod 47 of steel or like material somewhatsofter than the carbide. The rod is seated in a long orifice 48extending vertically into the cutter body through the forward cutterface 22a thereof. A bore 49 transversely intersecting orifice 47receives a locking pin 50 which alsoseats in a recess 51 in rod 47abreast of bore 49. Only one of the locking pins is shown in FIG. 6cooperating with a pair of the carbide. composites but eachof thecomposites may be similarly locked in position in the bit body. Pin 50can be removed and reinserted as through opposing wing chamfers 26 and27. A passage 52 opening into the bottom of orifice 48 may accommodate apressured fluid, as gun grease, for forcing rod 47 out of orifice 48.

FIGS. 8, 9, l0, and 11 illustrate another means for anchoring thecarbide element firmly in the bit body. In FIG. 8-, sleeve 41b,initially, has a generally cylindrical inner'surface 57 and'a conicalouter surface 53 tapering upwardly and outwardly from the smaller inneror bottom end 54. Carbide element 390 is tapered oppositely-to sleeveouter surface 53, that is, upwardly and inwardly from its larger baseportion 55, which fairly snugly fits within base portion 54 of thesleeve jacket, to its smaller outer or forward extremity 40a. When thisassembly is driven into an orifice in the body which is approximately ofthe diameter of the base portion 54 of sleeve 41b, the sleeve isdistorted or swaged, as illustrated in FIG. 11, to cause sleeve innersurface 52 to heavily encase carbide outer surface 56, thus locking boththe sleeve and the carbide firmly in position in the bit body. In orderto facilitate this action, sleeve 41b may be radially split as shown inFIG. 10. However, if inclines 53 and 56 are not too great, suchsplitting of the sleeve may not be necessary and the sleeve may beswaged into the distorted form shown in FIG. 11' upon the application ofsuitable pressure thereto. I v

The form in FIG. 9 is similar to that in FIG. 8 except for the provisionof a bottom web 58 in jacket 41c with outwardly tapered outer surface580. Carbide element 390 is the same as in the previous form, and themethod of firmly anchoring the carbide and sleeve into the body orificeis the same.

FIG. 12 showsa cup-likesteel jacket 60 receiving cylindrical carbidebutton 61 being driven into a snugly fitting orifice 62in the bit body63 by means'of a tubular punch 64. If desired,the punch may have a solidcentralpart, as suggested at 65, for insuring proper driving of carbideelement 61.

FIGS. 13 and 14 illustrate cutter insert composites including jacketparts of modified'polyhedral shapes of the carbide'cutters shown, forinstance, in Bassinger US. Pat. No. 2,976,944. In FIG. 13 there is showna jacket body 66 having a wedgeor roof-shaped cutter face 67terminatingin an edge 68. In the Bassinger patent, as in other prior artdevices, member 66, 67 is itself formed of hardened carbide cuttermaterial, and edge 68 is the cutting edge. However, in the presentinstance member 66, 67 is of steel or other softer 'machinable materialwhich may be readily secured in the body metal of the bit as by silversoldering. Projecting into the apex of roof part 67 are a plurality ofcarbide cutter insert buttons 69 which are pressfitted into orifices 70in body 66, 67. Additional carbide inserts are shown at 71 and 72.

In FIG. 14 the body 66a, 67a is provided with a slot 78 depending fromthe apex in which is firmly seated a plate-like carbide cutter element73. In both of the latter forms, the carbide cutter element can beremoved by cutting away of the body part 66, 67 or 66a, 67a by suitablemachining operation which may be effected without damaging the bit bodyitself.

FIG. 15 illustrates a method of manufacturing the carbide compositeinserts. An elongated sleeve 75 of steel or other sufficiently ruggedyet drillable material is provided with a filler 76 of tungsten carbideconveniently inpowdered form and then solidified as with the use of heatand pressure. Alternatively, the jacket sleeve may be silver soldered orsweated on a solid carbide core. The long carbide composite is then cutinto longitudinal sections commensurate with the desired length of thecomposite insert. In addition to a convenient manufacturing method, thisform insures complete encasement of the carbide filler, an advantageover conventional practice in which the carbide insert frequently ispressed .in a bell-mouthed orifice which, therefore, fails to supportand protect the full length of the insert within the orifice.

FIGS. 16 and 17 illustrate a form of insert composite in which theinternal carbide element 75 is star-shaped and snugly fits within asimilarly shaped orifice in drillable jacket 76. The carbide can beremoved by trepanning around the star points. Alternatively, thecomposite 75, 76,the latter being cup-shaped, may be removed byproviding a'plug 77 of material as lead of greater thermal expansioncoefficient than bit body 78 or jacket 76 inan extension of bore 79 inthe body, inwardly of the composite insert. When it is desired to removethe insert, the bit body is heated sufficiently to cause the lead plugto push the insert slightly outwardly of its orifice. The insert thencan be grasped by a gripping tool and withdrawn from the bore. Variousnoncircular carbide shapes may be utilized for the purpose, forinstance, of increasing the contact surface area between the carbide andjacket and thus, the bonding or frictional efficiency.

It is contemplated that the drillable sleeve or other jacket be merelyof adequate size to mount a carbide insert or several of them, as, forinstance, in FIG. 13, and that this jacket will then be suitably securedwithin the bit body either by a press fit or by brazing or silversoldering technique. The armoring jacket maintains the carbide insertunder firm compressive forces so as to support and protect the elementagainst chipping or breakage. The preferred form utilizes a cylindricaljacket, as in FIG. 4, for instance, which is best adapted for removal bya trepan or crown saw operation. Such saw may be guided by the carbide,particularly if the carbide is cylindrical, and may remove at least theouter portion of the sleeve so that the entire sleeve jacket and carbidemay be withdrawn. The exclusive use of all modifications as come withinthe scope of the appended claims is contemplated.

I claim:

1. A rock bit comprising body structure having a cutting face, ahardened, substantially non-machinable cutter element extending into andseated in said body structure and projecting beyond said face, and aprotective jacket interposed between and firmly anchoring said elementin said structure, said'jacket being of machinable metal, beingsubstantially non-yieldable radially, and being annular so as to beremovable from said structure by an annular milling cutter withoutdamaging said structure.

2. A rock bit as described in claim 1 further including a bore in saidbody structure in which said jacket snugly fits and in which said jacketis provided with a generally radial, longitudinal slot in its outersurface to facilitate removal of said jacket by a trepanning operationwithout damaging the surface of said bore.

3. A rock bit as described in claim 1 in which said jacket and saidcutter element have oppositely tapering, generally conical outer wallsand said jacket is radially split to facilitate the collapse of saidjacket and anchoring of said composite in said body structure bore.

1. A rock bit comprising body structure having a cutting face, ahardened, substantially non-machinable cutter element extending into andseated in said body structure and projecting beyond said face, and aprotective jacket interposed between and firmly anchoring said elementin said structure, said jacket being of machinable metal, beingsubstantially nOn-yieldable radially, and being annular so as to beremovable from said structure by an annular milling cutter withoutdamaging said structure.
 2. A rock bit as described in claim 1 furtherincluding a bore in said body structure in which said jacket snugly fitsand in which said jacket is provided with a generally radial,longitudinal slot in its outer surface to facilitate removal of saidjacket by a trepanning operation without damaging the surface of saidbore.
 3. A rock bit as described in claim 1 in which said jacket andsaid cutter element have oppositely tapering, generally conical outerwalls and said jacket is radially split to facilitate the collapse ofsaid jacket and anchoring of said composite in said body structure bore.